add Functor (#40)

Author: d1skort

MonadTransformers/4.4/Functor2.hs

@@ -0,0 +1,16 @@
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE FlexibleInstances #-}
+module Functor2 where
+
+
+class Functor' c e | c -> e where
+  fmap' :: (e -> e) -> c -> c
+
+
+instance Functor' (Maybe e) e where
+  fmap' _ Nothing  = Nothing
+  fmap' f (Just x) = Just $ f x
+
+
+instance Functor' [e] e where
+  fmap' = map